Sheet feeding device

ABSTRACT

A sheet feeding device includes a stacking plate, a pick-up device, means for blowing air, and a holding member. On the plate, sheets to be fed into a processing apparatus are placed. The device sends out a top one of the sheets placed on the plate, and has a pick-up roller to be brought into contact with an upper side of the top sheet at a position within a predetermined level range when the sheet is to be fed into the apparatus. The means blows air to the sheet with a predetermined force in a direction to separate the sheet from the other sheets placed on the plate or from the plate. The member is to be brought into contact with the upper side at a position upstream of the roller with respect to a feeding direction in which the sheet is to be fed into the apparatus.

CROSS REFERENCE

This Nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2006-036414 filed in Japan on Feb. 14, 2006, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The invention relates to a sheet feeding device, such as a Large-Capacity Cassette (hereinafter referred to merely as LCC), adapted to store a large quantity of sheets to be fed into a sheet processing apparatus, such as an image forming apparatus, that performs predetermined processing on sheets.

Conventional LCCs are designed for installation beside a sheet processing apparatus and for storing sheets of a size most frequently used in the apparatus. Sheets stored in an LCC are sequentially sent out by a pick-up roller and fed into a sheet processing apparatus.

Because of their multifunctionality, however, recent image forming apparatus necessitate an LCC storing an increasing variety of kinds of paper, which can cause the pick-up roller to make picking-up errors. This is because different kinds of paper have different smoothness and therefore different surface resistance, and thus require the pick-up roller to apply different forces thereto. In other words, paper with a higher surface resistance requires a stronger force to be picked up with. For proper picking up of paper with a high surface resistance, the pick-up roller may be set to apply a strong force to paper to be picked up. However, the strong force makes a multifeeding problem more likely to occur with plain paper with a low surface resistance.

In view of the foregoing, the technology has been conventionally adapted of preventing picking-up errors of the pick-up roller by blowing up a sheet of paper to be picked up with air. In this regard, JP 2001-031273A discloses a sheet feeding device adapted to selectively blow air based on input information on the kind of paper.

In the conventional technology, however, paper is excessively blown up if air is blown to paper with a constant force when there is a small amount of paper stacked in the device. Thus, the conventional technology is associated with problems such as skewing of paper or paper jam.

Since the device as disclosed by JP 2001-031273A requires a user to input information on kinds of paper, meanwhile, incorrect information on kinds of paper input by a user causes paper to be excessively floated, resulting in skewing of paper, paper jam, or the like.

Thus, it becomes necessary to adjust a force with which air is to be blown to paper without using information input by a user. However, such adjustment involves complicated controlling processes, which result in an increase in production cost. In view of the recent, severe price competition, it is to be desired that a large-capacity sheet feeding device can be manufactured with a minimum increase in production cost.

A feature of the invention is to provide a sheet feeding device having a simplified configuration that prevents degradation in sheet transport performance, such as skewing of a sheet, while maintaining sheet separating performance.

SUMMARY OF THE INVENTION

A sheet feeding device is adapted for connection to a processing apparatus that performs predetermined processing on a sheet. The device includes a stacking plate, a pick-up device, means for blowing air, and a holding member. On the plate, sheets to be fed into the apparatus are placed. The device sends out a top one of the sheets placed on the plate, and has a pick-up roller to be brought into contact with an upper side of the top sheet at a position within a predetermined level range when the top sheet is to be fed into the apparatus. When the top sheet is to be fed into the apparatus, the means blows air to the top sheet with a predetermined force in a direction to separate the top sheet from the other sheets placed on the plate or from the plate. Also, the member is to be brought into contact with the upper side of the top sheet at a position upstream of the pick-up roller with respect to a feeding direction in which the top sheet is to be fed into the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of an LCC according to an embodiment of the invention and an image forming apparatus connected to the LCC;

FIG. 2 is a schematic front cross-sectional view of the LCC;

FIG. 3 is a partial enlarged cross-sectional view of the LCC;

FIG. 4A is an enlarged view illustrating a pick-up roller, and a holding member, out of contact with a top sheet;

FIGS. 4B and 4C are enlarged views illustrating the pick-up roller, and the holding member, in contact with a top sheet;

FIG. 5 is a partial enlarged top view of the LCC;

FIG. 6 is a schematic side cross-sectional view of an air blowing mechanism provided in the LCC;

FIG. 7 is a block diagram illustrating a schematic configuration of the LCC and an image forming apparatus connected to the LCC; and

FIG. 8 is a partial enlarged top view of an LCC according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic cross-sectional view of an LCC 1 according to an embodiment of the invention, and an image forming apparatus 100 to which the LCC 1 is connected. The LCC 1 is installed beside the apparatus 100. Instead of the single LCC 1 as in the present embodiment, a plurality of LCCs may be arranged in alignment with one another. The LCC 1 feeds a sheet of paper P, or another material such as OHP film, into the apparatus 100.

The apparatus 100 is provided with an image forming section 200 for forming an image on a sheet by performing an electrophotographic image forming process. The apparatus 100 is also provided with a sheet feeding section 300 and a sheet output tray 105. The section 300, which is positioned below the section 200, has sheet cassettes 101, 102, 103, and 104. The tray 105 is positioned above the section 200.

The apparatus 100 is provided with a sheet transport path F1 that leads from the cassettes 101, 102, and 103 to the tray 105. A photoreceptor drum 106 is positioned along the path F1. Around the drum 106 arranged are a charging device 107, an optical scanning unit 108, a developing unit 109, a transferring device 110, and a cleaning unit 111. Registration rollers 112 are located upstream of the drum 106 along the path F1. The rollers 112 feed a sheet of paper P to a transfer area between the drum 106 and the device 110 in synchronization with rotation of the drum 106. A fusing device 113 is provided downstream of the drum 106 along the path F1.

The device 107 applies a predetermined level of electrostatic charge to a circumferential surface of the drum 106. The unit 108 forms an electrostatic latent image on the circumferential surface of the drum 106 according to external input image data. The unit 109 supplies toner to the circumferential surface of the drum 106 to develop the electrostatic latent image into a toner image. The device 110 transfers the toner image from the circumferential surface of the drum 106 to the sheet of paper P. The unit 113 fixes the transferred toner image to the sheet P. The unit 111 removes and collects residual toner that remains on the circumferential surface of the drum 106 after the toner image is transferred to the sheet P. The sheet with the toner image fixed thereto is output to the tray 105.

The apparatus 100 is also provided with a switchback transport path F2 and a sheet transport path F3. In a duplex image forming process in which an image is formed on each side of a sheet of paper P, the path F2 serves to reverse a first and a second sides of the sheet with an image formed on the first side and then transport the sheet P to the transfer area. The path F3, which extends approximately horizontally, is used to feed a sheet from either one of the cassette 104, a manual feeding tray 114, and the LCC 1, to a confluence of the paths F1 and F3. The tray 114 is provided on a side surface of the apparatus 100 and used to place sheets of various sizes thereon. The LCC 1 is connected to the apparatus 100 through a sheet receiving section 115.

FIG. 2 is a schematic front cross-sectional view of the LCC 1. The LCC 1 includes a sheet stacker 2, a pick-up roller 3, a feeding roller 4, a reversing roller 5, and transporting rollers 6. The LCC 1 feeds a sheet of paper P in a direction or arrow Z to the apparatus 100.

The stacker 2 has a stacking plate 21, a front guiding plate 22, side guiding plates 23 and 24, and a rear guiding plate. The side guiding plate 24 and the rear guiding plate are not shown in the figure. The plate 21 is held in a horizontal position inside the stacker 2. A plurality of sheets of paper P are neatly stacked on the plate 21 by being positioned with the front guiding plate 22, the side guiding plates 23 and 24, and the rear guiding plate.

While being rotated, the roller 3 is brought into contact with a top one of the stacked sheets on the plate 21, i.e., a top sheet P1. Thus, the roller 3 picks up and sends the top sheet P1 out in between the rollers 4 and 5. A rotating shaft 3A of the roller 3 is coupled to a rotating shaft 4A of the roller 4 through a coupling belt 9. This coupling allows the roller 3 to be rotated together with the roller 4.

The roller 3 has a fixed shaft 3B secured to a supporting plate 4C. On the shaft 3B, the roller 3 and the shaft 3A are rotatably mounted. The plate 4C is pivotably mounted on a fixed shaft 4B of the roller 4. The shaft 4B is mounted on a frame of the LCC 1. On the shaft 4B, the roller 4 and the shaft 4A are rotatably mounted. Thus, the plate 4C allows the roller 3 to be pivoted up and down, about the shaft 4B, within a predetermined range that includes a specified level range D.

The roller 3 is urged upward by an elastic member (not shown). When the roller 4 is not being rotated, thus, the roller 3 is positioned at a highest level within the predetermined range. While the roller 4 is being rotated, meanwhile, the roller 3 is being rotated by the belt 9. The produced turning moment thereon causes the roller 3 to be lowered, against the urging force of the elastic member, and brought into contact with an upper side of a top sheet P1.

The sheet P1 is sent out by the roller 3 and passed between the rollers 4 and 5. The rollers 4 and 5 are both rotated in synchronization with each other in a clockwise direction shown in FIG. 2. In a case where the roller 3 picks up multiple sheets at a time and sends the sheets in between the rollers 4 and 5, only a top sheet P1 is brought into contact with the roller 4 and is led to the transporting rollers 6. The rest of the sheets are returned to the plate 21 by the roller 5.

A sheet sensor 11 (refer to FIG. 7) is mounted on an inner side surface of the LCC 1. The sensor 11 detects the level of a top sheet P1 within the range D.

When determining, based on the detection result of the sensor 11, that the sheet P1 is not positioned within the range D when the sheet P1 is to be fed, CPU 10 causes the plate 21 to be elevated to position the sheet P1 at a highest level within the range D.

In a case in which a plurality of sheets are to be successively fed into the apparatus 100, the CPU 10 causes the pick-up roller 3, the feeding roller 4, and the reversing roller 5 to be rotated only when each one of the sheets are being discharged from the LCC 1 to the apparatus 100. More specifically, the CPU 10 causes the rollers 3, 4, and 5 to be rotated only for the duration between the moment when a top sheet P1 is sent out by the roller 3 and the moment when a tail end of the sheet P1 passes through a contact area between the rollers 4 and 5. Then, the CPU 10 halts the rotation of the rollers 3, 4, and 5 until the time when a new top sheet P1 is to be sent out. The CPU 10 repeatedly starts and halts the rotations of the rollers 3, 4, and 5 to feed a plurality of sheets successively.

In a successive feeding operation, additionally, the level of top sheet P1 is gradually lowered as the sheets are being sent out successively. When determining that the level of top sheet P1 drops below the range D, the CPU 10 halts the rotation of the roller 4. At the time, the roller 3 is raised and brought out of contact with the sheet P1. Then, the CPU 10 causes the plate 21 to be elevated. When determining, based on the detection result of the sensor 11, that the sheet P1 is positioned at the highest level in the range D, the CPU 10 causes the roller 4 to be rotated again, thereby causing the roller 3 to send the sheet P1 out.

To the shaft 3B, a holding member 40 is connected through a connecting member 41. The member 40 has a cylindrical shape as shown in FIGS. 3 and 5. When in contact with an upper side of a top sheet P1, the member 40 is positioned upstream of the roller 3 with respect to the direction of arrow Z. With an axis perpendicular to the direction of arrow Z, the member 40 is fixed to the member 41 so as to be pivoted together with the roller 3.

The member 41 is pivotably mounted on the shaft 3B. Referring to FIGS. 4A and 4B, the member 41 has a stopper pin 42A fitted through a guiding hole 42B formed in the plate 4C. In other words, the member 41 is pivotable within a range restricted by the hole 42B.

When the roller 3 is in a position out of contact with a top sheet P1 as shown in FIG. 4A, the member 40 is at a distance from a top sheet P1 with the pin 42A in a lowest portion of the hole 42B.

When the roller 3 is lowered to a position within the range D to have contact with an upper side of the sheet P1 as shown in FIGS. 4B and 4C, meanwhile, the member 40 is pivoted about the shaft 3B and brought into contact with the upper side of the sheet P1. Thus, the member 40 is brought into and out of contact with the upper side of sheet P1 along with the roller 3.

When in contact with an upper side of top sheet P1, the member 40 is positioned within an area of the plate 21 where sheets of minimum size are to be placed. The positioning allows the member 40 to be brought into contact with an upper side of sheet P1 of minimum to maximum sizes to be placed on the stacking plate 21.

It is preferable that the member 40 has a cylindrical, spherical, or similar shape such that at least a surface of the member 40 to have contact with an upper side of sheet P1 (hereinafter referred to as the contact surface) is curved. This is because the curved contact surface causes less friction with the sheet P1 and thus less negative effects on sheet transport performance. Similarly, less negative effects on sheet transport performance may also be caused by supporting the member 40 rotatably so that the contact surface is rotated in the direction of arrow Z.

The positioning and number of the member 40 include, but are not limited to, those shown in FIG. 5. As an example, a plurality of holding members 40 may be arranged as shown in FIG. 8. Also, the member 40 may be supported by the frame of the LCC 1 or the like, instead of by the connecting member 41 as in the present embodiment.

Further, it is to be noted that the feeding roller 4 and the reversing roller 5 collectively correspond to the separating member of the Claims. Furthermore, the pick-up device of the Claims includes the pick-up roller 3, the coupling belt 9, the feeding roller 4, and the reversing roller 5.

The LCC 1 has a capacity of a large number of sheets (approximately 5,000 sheets in the present embodiment) of various sizes such as of A3, B4, A4, and B5.

On the plate 21, thus, the side guiding plates 23 and 24 are rendered movable within a predetermined range along a direction of arrow W (as shown in FIG. 5) that is perpendicular to the direction of arrow Z. Movement of one of the plates 23 and 24 in one direction is transmitted to the other one so that the other one is moved in the opposite direction. Accordingly, sheets stacked on the plate 21 are positioned approximately around the center of the plate 21 with respect to the direction of arrow W. On the plate 21, in addition, the rear guiding plate is rendered movable within a predetermined range along the direction of arrow Z.

The stacker 2 has a lifting motor (not shown) mounted on a rear side surface. Rotation of the lifting motor is transmitted through wire, so that the plate 21 is moved up and down along a guiding shaft (not shown) while being held in a horizontal position. Inside the LCC 1, there are provided slide rail assemblies 7 and 8. Each of the assemblies 7 and 8 has its components mounted over the inner side surface of the LCC 1 and an outer side surface of the stacker 2.

FIG. 6 is a side cross-sectional view illustrating a schematic configuration of an air blowing mechanism. The air blowing mechanism corresponds to the means for blowing air of the Claims. The mechanism includes an air blower 19, ducts 16A and 16B, and openings 18A and 18B. The openings 18A and 18B are provided in the side guiding plates 23 and 24, respectively. The blower 19 is a fan for blowing air with a predetermined force. The ducts 16A and 16B guide therethrough the airflow created by the blower 19, to a top sheet P1. The ducts 16A and 16B are connected to the plates 23 and 24, respectively. The openings 18A and 18B allow the airflow guided through the ducts 16A and 16B to be introduced into the level range D.

FIG. 7 is a block diagram illustrating a schematic configuration of the LCC 1 and the image forming apparatus 100. The apparatus 100 has CPU 150, ROM 151, RAM 152, the image forming section 200, the sheet feeding section 300, an operating section 400, and a transport detection sensor 15. The apparatus 100 is connected to the LCC 1.

The CPU 150 has overall control of the components of the apparatus 100. The ROM 151 stores therein programs required for the apparatus 100 to perform various operations. The RAM 152 is a volatile memory for holding data temporarily. The section 400 has an operating panel and a liquid crystal display (LCD). The operating panel provides a user interface across which a user inputs commands or the like. The LCD presents information to the user. The sensor 15 detects a sheet being passed on the sheet transport path F3.

The LCC 1 is provided with a sheet feeding mechanism 13, the sheet sensor 11, a driver 12, the air blower 19, and the CPU 10. The CPU 10 has overall control of the components of the LCC 1. When the feeding roller 4 and the pick-up roller 3 are rotated in a sheet feeding operation, the CPU 10 activates the blower 19 through the driver 12. When the rotation of the rollers 4 and 3 is stopped in the sheet feeding operation, the CPU 10 deactivates the blower 19 through the driver 12. In other words, the CPU 10 holds the blower 19 activated only while a top sheet P1 is being sent out.

Thus, the sheet P1 to be fed into the apparatus 100 is blown up with the air from the blower 19. Also, the sheet P1 is sent out by the roller 3, with an upper side thereof in contact with the holding member 40. More specifically, the sheet P1 is held down by both of the rollers 3 and 4. This prevents the whole sheet P1 from being blown up with the air from the blower 19, thereby preventing the sheet P1 from becoming skewed while being sent out.

Furthermore, a portion of the sheet P1 positioned upstream of the roller 3 with respect to the direction of arrow Z is held down by the member 40. Thus, at least a leading portion of the sheet P1, which is positioned on the side of the roller 3, is blown up with the air from the blower 19. This facilitates separation of only the sheet P1 from the rest of sheets of paper P.

Thus, degradation in sheet transport performance is prevented while sheet separating performance is maintained.

FIG. 3 shows sheets of minimum-size paper P stacked on the plate 21. It is to be noted that the minimum paper size is B5 in the present embodiment. Referring to FIG. 3, a distance X between a position in which the member 40 is in contact with an upper side of top sheet P1 of the minimum-size paper and a tail end of the sheet P1 along the direction of arrow Z is set larger than a horizontal distance Y between a leading end of the sheet P1 along the direction of arrow Z and a separating position in which the roller 4 is in contact with the roller 5. Thus, the sheet P1 is allowed to be delivered to the separating position while in contact with both of the roller 3 and the member 40. This prevents a top sheet P1 of all storable sizes from being floated too high before being delivered to the separating position, thereby maintaining a separating performance.

Regarding an LCC designed to store sheets of paper of a single size only, meanwhile, advantageous effects similar to those as described above can be achieved when the distance X is set larger than the distance Y with respect to the given paper size.

It is to be noted that the invention is applicable not only to the LCC 1 that is adapted to blow air to a top sheet P1 with a constant force, but also to a sheet feeding device provided with additional means for adjusting force with which to blow air.

It is to be also noted that the invention is applicable not only to the LCC 1 that is designed for installation beside the apparatus 100, but also to a sheet feeding device designed for installation inside the apparatus 100 or designed for use with a sheet processing apparatus, other than the apparatus 100, for performing predetermined processing on a sheet.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. 

1. A sheet feeding device adapted for connection to a processing apparatus that performs predetermined processing on a sheet, the sheet feeding device comprising: a stacking plate for placing thereon sheets to be fed into the processing apparatus; a pick-up device for sending out a top one of the sheets placed on the stacking plate, the pick-up device having a pick-up roller to be brought into contact with an upper side of the top sheet at a position within a predetermined level range when the top sheet is to be fed into the processing apparatus; means for blowing air to the top sheet, when the top sheet is to be fed into the processing apparatus, with a predetermined force in a direction to separate the top sheet from the rest of the sheets placed on the stacking plate or from the stacking plate; and a holding member adapted to be brought into contact with the upper side of the top sheet, when the top sheet is to be fed into the processing apparatus, at a position upstream of the pick-up roller with respect to a feeding direction in which the top sheet is to be fed into the processing apparatus.
 2. The sheet feeding device according to claim 1, further comprising a connecting member for connecting the holding member to a rotating shaft of the pick-up roller in such a manner that the holding member is pivotable within a predetermined range, wherein the pick-up device has a mechanism for moving the pick-up roller, up and down within a range that includes the predetermined level range, to bring the pick-up roller in and out of contact with the upper side of the top sheet.
 3. The sheet feeding device according to claim 1, wherein: the stacking plate is adapted for sheets of a single size to be chosen from multiple sizes, to be placed thereon, and the holding member is brought into contact with the upper side of the top sheet within an area of the stacking plate where a sheet of smallest size chosen from the multiple sizes is to be positioned.
 4. The sheet feeding device according to claim 2, wherein: the pick-up device has a separating member for separating the top sheet from any other sheets sent out by the pick-up roller, at a separating position downstream of the pick-up roller with respect to the feeding direction, and a distance between a position where the holding member is brought into contact with the upper side of the top sheet and a tail end of the top sheet along the feeding direction is set larger than a distance between the separating position and a leading end of the top sheet along the feeding direction.
 5. The sheet feeding device according to claim 2, wherein: the stacking plate is adapted for sheets of a single size to be chosen from multiple sizes, to be placed thereon, the pick-up device has a separating member for separating the top sheet from any other sheets simultaneously sent out by the pick-up roller, at a separating position downstream of the pick-up roller with respect to the feeding direction, and a distance between a position where the holding member is to be brought into contact with an upper side of a top one of sheets, of smallest size chosen from the multiple sizes, placed on the stacking plate and a tail end of the top sheet along the feeding direction is set larger than a distance between the separating position and a leading end of the top sheet along the feeding direction.
 6. The sheet feeding device according to claim 1, wherein the holding member has a curved surface to be brought into contact with the upper side of the top sheet.
 7. The sheet feeding device according to claim 5, wherein the holding member has a cylindrical or spherical shape and is supported rotatably about a horizontal axis perpendicular to the feeding direction. 